I think the Harmony has better single coat coverage and it's zero VOC, so your project smells better sooner.

I started small and got the confidence which is 80% of the battle.

The house would start to fill with the smell of pine wood burning like with a power saw and also filled with blue smoke.

If you go down to a C- property in a dicey area you'll eventually hit a "$5K turnover" because you walk in and there are random holes in the drywall, torn-up carpet, a weird smell, etc.  

I did it once, went out of my way to make sure it was 100% waterproof, and still 6 months later it started to smell like mold and I ripped it all out.

Assuming there would be no physical damage (burns in carpet, etc.) there is still the smell of smoke in the unit which can obviously deter any future renters.

Along with any risky undertaking comes a measure of doubt, and I battled with monkeys in my head concerning what my niche would be.

In all of my other units, I prohibit smoking (and cats) for the sake of unpleasant odors and allergens, etc...How tough is it to remove smoke smell? 

As far as smell goes, if they keep the cage clean  it shouldn't be a problem.

They ripped out all the old carpeting, and it already smells a lot better.